This project focuses on the neural basis of perceptual learning in visual cortex. Although plasticity has been well documented in visual cortex, the time course of plasticity and the kinds of changes that occur in visual neurons have not been fully characterized. The proposed experiments aim to explore the development and nature of visual plasticity due to extensive training by monitoring the evolution of cortical neuronal responses relative to the time course of behavioral change. The change of psychometric and neurometric contrast response functions and the change in correlation within neuronal ensembles will be explored as more sensitive measures of plasticity. An understanding of the mechanisms of change in the cerebral cortex as a result of training is potentially very important for the medical treatment of humans with various kinds of brain damage. In particular, the treatment of strokes and other focal brain lesions can gain insight from the research in this proposal. In addition, knowledge of the limits of visual cortical plasticity are important in understanding diseases such as amblyopia, in which there are known changes in the cortex as a result of a visual impairment.